Process for mechanically corroding relief intaglio variegated surfaces on metal



Sept. 18, 1934.

J. J. BURGESS PROCESS FOR MECHANICALLY CORRODING BELIEF INTAGLIO VARIEGATED SURFACES ON METAL Filed May 16, 1932 JO N J BURGESS Patented Sept. 18, 1934 PROCES S FOR? MEGHANIQALLY; CDREQDING BELIEF INTAGLIB VARIEGA-'EE D SUR FAoEs ON.. METAL John J; Burgess, Rock Island; III., assignor to Rock Island Register.- Company, Rock' Island;` Ill.,.a ccrporat-ion; of Illinois "Application May. 16,. 1932, Seriali No; &11,695

3 Claims.

This' inventi'on relates to a process for me chanically corroding. relief intaglio: variegated;

surfaces on metallic sheets or' metallic: articles;

either before' or after fabrication for the pur- 5 pase' of. producing` an ornamental: erratic pattern or` surface' in relief which; is permanent,

since it is etched in the metal' itself, andcapableof beingxgivena color effects as. d'esired, by ordinary processes of electro-plating, the application of lacquer, etc.

The principal object. of the invention is the provision of an etching process for producing the ornamental intaglic surface as above described, characterized by thefact that while the general motif of the design or pattern is controlled by a. protective spotting,. manually applied, and of such elemental nature as to require but a modicum of skill on the part of the operaton the` conditions of the etching are such as to cause the acid to break from the restraint imposed by the manual spotting and to underbite said spotted areas imparting irregular, indented, devious outline to the high relief areas produced by the. spotting, materially changing their shapes so that they are by no means replicas of the original spotting, but assuming shapes which are practically inimitable by hand work, and de.- pending but little upon the skill of the operator who did the spotting. At the same time, the acid bites depthwise in an erratic manner into the unprotected areas producing reliefs of different levels and leaving the contours of the surface in a Very irregular condition.

Another object of the invention is the provision of the process as above described in which by applying the protective coating in Spots of diiferent degrees of coverage, different and vagarious relief eflects are obtained.

A further object of the invention is the pro- Vision of an etching process including in combination with the spotting of the surface to be processed, as described, the step of 'ooating the unprotected portion of the surface with sponge copper autogenously derived from the etching bath, said coating acceleratirg the Corrasive action of the acid, and causing the erratic and irregular biting of the underlying surface and the lateral biting of the margins beneath the spotted areas. e

Other objects of the invention will appear as the following description of a preferred and practical embodiment thereof proceeds.

In the drawing which accompanies and forms a part of the following specification and throughout the several figures of which the samecharacters, of reference; have] been eme. ployed to designate identical parts E urezlgis a; plan viewsof; &metal sheetg illus; t at n somewhat; dia anma i al he; na ure of the variegatedsrface; v

'Figure 2: is; a` vertical ;section through a por-, t-ion: of: a metal; .plate showing one i side covered by a. protective coating and the; other side. in terspersedi with spots of; the protective-coating, of: various; degrees of contimityof; coverage; i

Figuresiis a, sectionalview showing the metal; ini the: etching bath; and:

Eigure 4: is a, plan. View partly diagramn atig illustrating.: the manner inwhich the acid under; bit'es the ed'ges. of the original: spotting.

Referring nowin detaili to the severalfigures the numeral' 1 represents a, metal sheet,-s t el f'orexampl'e. To: pr pare it for: theproc ss it is first cleanedvin any suitable known; man order tofr-ee. it from. grease. 'Dhe back surface or those: parte. which. it is desir d shall: be left; in their original: state is; coated with a suitable protective material: such for instanc as. a phalt orbitumen. 'lhe face. side or. thatsurfacew i is: to' be processed is. spotted' with various small areas of asphalt or the like, preferably, although not necessarily, applied with a stif` bristled brush and different degrees, of coverage, that is to` say, some' of the Spots: being solid uhbroken areas: while others are striated bythebristles of the brush-` The asphalt, is dried; eitherat atmospheric temperature in the air, or in an oven ata suitable heat. In the illustrative embodiment of" the invention as herei-n described; an air drying for two hours or. drying for one: half hour at a temperature of- 200 F; is recom: mended r The metal sheet thus preparedis then 'subjeeted to a bath in an aqueous solution of copper sulphate and sulphuric acid. The solution may be made by dissolving the Copper sulphate in Water until thefsclution stands at froni 128 to 20 Baum or until the solution is saturated'. The sulphuri acid is then added, stirringlit until the solution' stands at from .2 Q to 39. Baum. f

In Figure 2, the solidly` spotted areas are designated by the reference character 2 ,whi 1 e the reference numeral 3` indicates a spotted area less solidly ccat d an whic w l v etua y p undercut by the acid and bitten to a lower re: lief than t e urfa e uns r s h m re. cl coating 2.

The back of the plate 1 is shown .protected by a uniform layer 4 of bitumen or any suitable acid-resistant coating.

When the sheet prepared with the protective spotting is immersed in the etching bath, a thin spongy. coatingvof copper Will formon that part or those parts not covered by the asphaltum and Will stay on the unprotected surface as long as the operation is in progress. The copper sponge acts by capilarity to bring and hold the solution against the material, making it active and erratic, causing a corrosion which leaves the attacked surface in a very irregular condition.

ri those parts which` are coated with the asphalt, the corrosion takes place at a rate: varying With the nature of the spotting. The

parts to which the asphalt has been applied solidly, will be less attacked depthwise by the solution, than parts where it is applied in striated areas, and of course, where there is no asphalt the solution attacks the surface a great deal faster, thus bringing out the many and varied designs and figures. The margns of the coated areas Will be attacked laterally by the acid, the latter eating'in' under the asphalt and defining shapes which are quitedifferent from the shapes of'the areas as spotted' Some parts of theunprotected surface will beunder-bitten by the -ac`id, thus' leaving lights and shadows in the finished product. Thesurface. will be leftin reliefs of different elevations, those parts which are the more completely protected by the asphalt' being in high relief while the parts less fully protected will stand at a lower level.

There is" not much left to the skill of the operator, The chemical action of the solution reacts differentlyover the entire surface of the material. ;No two pieces are exactly alike and never like the designs applied with the asphalt r or bitumen', eventhough the asphalt spotting on two pieces Were done substantially. alike.

'Figure-B illustrates what takes place in the acid bath. The sheet 1 is shown immersed in the etching solution 5. The unprotected surface 6 is shown covered with a layer of sponge copper. Beneath this layer the surface is shown at 7 eaten away both depthwise and laterally beneath the adjacent protected areas.

In Figure 4 the areas 2 represent the original coated spotting. The areas 8 bounded by the broken lines indicate the shapes of the eventuating reliefs caused by the lateral biting of the acid beneath the protected areas. The transversely shaded areas in Figure 1 represent the Originally unprotected surface of the sheet plus the laterally attacked margins of the spotted areas, differences in character of the hatching indicating the vagarious irregularities incident to the action of the acid through the sponge copper.

The sheets are left in the solution from six to twelve hours, depending upon the desired effects. Upon removal from` the bath, the sheets or articles are immersed, in a hot lye solution for the removal of the asphalt. They are then brushed with pumice and water or an equivalent detergent which removes the copper sponge, cleanses the surface and leaves it in the relief intaglio varegated condition to be considered either a finished product, or ready for any further finish or color application that one may desire to apply.

^ Wh' e the drawing illustrates the processing of only one side of the sheet, it is obvious that both sides can be processed' by' spotting each side and treating the material in every way the same as has already been described.

It is also possible to nickel-plate that side or those parts of the material which it is not desired to process, by first coating with the bitrimen or asphalt the portions which it is desirett to process and then electroplating the exposedl surfaces with nickel, This Will prevent action'. of 'the etching solution upon the parts so plated. The asphalt is then cleaned from the side intended for processing, and it is then spotted and processed in the manner hereinbefore described.

While I have in the above specication disclosed what I believe to be a preferred and practical embodiment of the invention, it is to be understood that the specific requirements of the process such for instance, as the drying? time, the nature of the material used for the protective coating, the strength of the solution, and the expedients employed to protect the parts not to be processed and to remove. the sponge copper and the asphalt or bitumen from the processed surface after the completion of the etching, are merely illustrative and'not to'-` be considered as limiting the scope of the inventon as claimed.

What I claim is:

1. Process for chemically corroding relief.` intaglio variegated surfaces'on rmetallic bodies comprising applying to a metallic surface a desultory spotting of acid resistant' material, and subjecting the resist spotted plate'to a solution of a metallic salt and acid whereby a pervious coatingof sponge metal is formed on the exposed portion of the surface and' an irregular etchng of said exposed surface 'depthwise and laterally beneath the margins of the spotted areas is produced through the erratic accelerat.- ing capillary action of the 'pervious sponge metallic coating. j

' 2. Process for chemically corroding relief intaglio variegated surfaces on metallic bodies comprising applying to a metallic surface a desultory spotting of said resistant material and subjecting the resist spotted plate to a solution of copper sulphate and sulphuric acid whereby a pervious coating of copper derived from said solution is formed on the exposed portion of said surface, and an irregular etching of theexposed surface depthwise and laterally beneath the margirs of the spotted areas is produced through theterratic accelerating capillary action of the pervious copper coating. r

3. Process for chemically corroding relief intaglio variegated surfaces on metallic bodies comprising spotting a metallic surface 'in desultory manner with acid ,resistant material in areas of different degrees of coverage, and subjecting the resist spotted plate to a solution of copper sulphate and sulphuric acid thereby simultaneously forminga pervious coating of cop-` per on the exposed portion of the surface, and irregularly etching the exposed surface depthwise and laterally. beneath the margins of the spotted areas, through the erratic accelerating capillary action of the pervious copper coating, and continuing the etching until the spots of least coverage have been under eaten by the acid.

v JOHN J; BURGss.

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